JP2007124328A - Antenna and wiring board - Google Patents

Abstract

An antenna that is small in size and high in performance and easy to manufacture and a multilayer wiring board incorporating the antenna are realized.
An antenna 1 built in a multilayer wiring board 2 includes radiating elements 11-1, 11-2, 11-3 and 11 laid on the surfaces of layers A, B and C of the wiring board 2, respectively. -4 and the radiating elements 11-1, 11-2, 11-3, and 11-4, power feeding units 12-1, 12-2, and 12-are respectively installed on the surface of the layer. 3 and 12-4, and short-circuit portions 13-1 and 13-2 respectively laid on the surface of the layer in order to ground each radiation element 11-1, 11-2, 11-3 and 11-4 , 13-3 and 13-4 and the layers A, B and C of the wiring board 2 are provided so as to be electrically connected to the power feeding units 12-1, 12-2, 12-3 and 12-4. Connecting portion 14 to be provided.
[Selection] Figure 1

Description

  The present invention relates to an antenna built in a multilayer wiring board and the wiring board.

  With the advancement of wireless technology, there is a further demand for improvement in characteristics such as antenna frequency band and gain, and miniaturization of the antenna structure. 8A and 8B are diagrams showing a general λ / 4 wavelength antenna. FIG. 8A shows a monopole antenna, FIG. 8B shows an inverted L-type antenna, and FIG. 8C shows an inverted F-type antenna.

  For the purpose of downsizing the monopole antenna shown in FIG. 8A, an antenna obtained by bending the radiating element in the middle to lower the posture is the inverted L-type antenna shown in FIG. 8B. The inverted L-type antenna has a drawback that the Y portion of the radiating element in the figure cannot be made so small. The reason for this is that as the Y portion of the radiating element is reduced, the capacitance component increases between the X portion of the radiating element and GND (ground). As a result, the reactance component of the antenna changes, and the power feed This is because impedance matching between the antenna and the antenna is broken. Therefore, there is a limit to downsizing the inverted L-type antenna.

  In order to facilitate impedance matching of the inverted L-type antenna, an antenna having a structure in which a short-circuit portion is provided in the vicinity of the feeding portion is an inverted F-type antenna shown in FIG. Inverted F-type antennas have the characteristic of radiating both vertically polarized waves and horizontally polarized waves, and are applied to various wireless small devices such as mobile phones as small omnidirectional antennas. . FIG. 9 is a basic principle diagram of a general inverted-F antenna. The L part in the figure determines the frequency of the inverted F-type antenna 50. A reactance component is formed in the vicinity of the region α by short-circuiting the radiating element 52 to the GND in the vicinity of the feeding portion 51, with respect to the capacitance component in the vicinity of the region β formed by bringing the L portion closer to GND. Impedance matching is intended. In addition to the planar type shown in FIG. 9, the inverted F type antenna includes a three-dimensional type as shown in FIG. FIG. 10 is a perspective view illustrating a general three-dimensional inverted F-type antenna. In the solid inverted F-type antenna 50 as well, the radiating element 52 is short-circuited to the GND in the vicinity of the power feeding unit 51 as in the planar type.

  As an antenna aimed at further miniaturization, there is an antenna in which an inverted L-type antenna and an inverted F-type antenna are combined (for example, see Patent Document 1).

  In addition to this, several antennas have been proposed in which the antenna configuration is reduced while maintaining and improving the antenna characteristics (see, for example, Patent Documents 2 and 3).

JP 2003-124742 A JP 2005-110109 A JP 2005-110110 A

  In the conventional technique described above, the antenna body can be downsized to some extent, but further downsizing is difficult. For example, the antenna described in Japanese Patent Laid-Open No. 2003-124742 (the above-mentioned Patent Document 1) has a structure equivalent to an inverted L-type antenna, and thus there is a limit to downsizing.

  In general, a large antenna has better antenna characteristics, and the antenna characteristics decrease as the antenna is miniaturized. Arraying is also conceivable as a solution for improving antenna characteristics, but there is a problem that the area occupied by the antenna increases and it is difficult to reduce the size.

  In addition, miniaturization of a wireless small-sized device incorporating an antenna is expected to continue further in the future, and it will be more difficult to incorporate the antenna in the manufacturing process of the device.

  Therefore, in view of the above problems, an object of the present invention is to provide a small, high-performance antenna that can be easily manufactured and a wiring board that incorporates the antenna.

  In order to achieve the above object, in the present invention, in a multilayer wiring board, a radiating element of an antenna is laid on each layer of the wiring board. That is, in the first aspect of the present invention, the antenna built in the multilayer wiring board includes a radiating element laid on the surface of each layer of the wiring board and a power supply to each radiating element. In order to ground each radiating element, a power supply section laid on each surface of the circuit board, a short-circuit section laid on the surface of the layer, and a layer through the wiring board. A connecting portion for electrical connection.

  In each layer of the wiring board, an inverted F-type antenna including a radiating element, a power feeding unit, and a short-circuit unit is formed. The feeding parts of the inverted F-type antenna formed on each layer of the wiring board are connected to each other by a connecting part provided through each layer of the wiring board. The connecting portion is formed of, for example, a through hole, but may be a conductive member having another configuration or shape.

  Each radiating element preferably has a different length. Thereby, a wide frequency band can be secured.

  Further, it is preferable that the radiating element, the power feeding portion, and the short-circuit portion are patterned for each layer of the wiring board. For example, in a manufacturing process of a wiring board incorporating an antenna, a wiring pattern of each layer of the wiring board is formed, and at the same time, a radiating element, a feeding portion, and a short-circuit portion constituting an inverted F-type antenna are formed.

  As described above, the multilayer wiring board incorporating the antenna according to the first aspect of the present invention includes a radiating element, a power feeding part for feeding power to the radiating element, and a short-circuit part for grounding the radiating element. And an inverted F-type antenna laid on the surface of each layer of the wiring board, and a connection that is provided through each layer of the wiring board and electrically connects each feeding portion A section.

  An antenna according to a second aspect of the present invention includes a plurality of radiating elements, a feeding unit that feeds power to each radiating element, and a short-circuit unit that connects each radiating element and the ground plane, and the plurality of radiating elements and feeding unit. And an inverted F-type antenna composed of a short-circuit portion. Here, it is preferable that the radiating elements have different lengths.

  According to the present invention, it is possible to realize a small-sized, high-performance antenna that is easy to manufacture and a multilayer wiring board that incorporates the antenna. Since the antenna is included in the wiring board having the module function, it contributes to further miniaturization and higher functionality of the wireless small device.

  In addition, in the manufacturing process of the wiring board incorporating the antenna, since the wiring pattern of each layer of the wiring board can be formed, the radiating element, the feeding part and the short-circuiting part constituting the inverted F-type antenna can be formed. It is possible to realize a reduction in manufacturing time and a reduction in manufacturing cost of a small wireless device including an inverted F-type antenna and thus an inverted F-type antenna.

  In addition, according to the present invention, it is possible to ensure a wide frequency band by making the radiating elements have different lengths. If the length of each radiating element is the same, the gain is improved. The antenna according to the present invention has a structure in which a plurality of inverted F-type antennas are stacked, so that the antenna characteristics are improved without changing the occupied area of the antenna compared with a conventional independent inverted-F antenna. Can be made.

  FIG. 1 is a perspective view of an antenna and a wiring board according to a first embodiment of the present invention. As an example, the case where the antenna 1 is built in a three-layer wiring board is shown. However, the application of the present invention is not limited to this three-layer, and can be applied to any number of layers of the wiring board. is there. FIG. 2 is a perspective view showing an inverted F-type antenna formed on the upper surface of the uppermost layer of the three-layer wiring board shown in FIG. FIG. 3 is a perspective view showing an inverted F-type antenna formed on the upper surface of the middle layer of the three-layer wiring board shown in FIG. 4 is a perspective view showing an inverted F-type antenna formed on the upper surface of the lowest layer of the three-layer wiring board shown in FIG. FIG. 5 is a perspective view showing an inverted F-type antenna formed on the lower surface of the lowest layer of the three-layer wiring board shown in FIG. Hereinafter, for convenience, among the three layers of the wiring substrate 2, the uppermost layer is referred to as A layer, the middle layer is referred to as B layer, and the lowermost layer is referred to as C layer.

  On the upper surface of the A layer that is the uppermost layer of the three-layer wiring board 2, the radiation element 11-1, the power feeding unit 12-1 for feeding power to the radiation element 11-1, and the radiation element 11-1 are grounded. A short-circuit portion 13-1 is laid so as to form an inverted F-type antenna. Further, on the upper surface of the B layer, which is the middle layer of the wiring board 2, to ground the radiating element 11-2, the power feeding section 12-2 for feeding power to the radiating element 11-2, and the radiating element 11-2. Are laid so as to form an inverted F-type antenna. Further, on the upper surface of the C layer which is the lowest layer of the wiring board 2, to ground the radiating element 11-3, the power feeding portion 12-3 for feeding power to the radiating element 11-3, and the radiating element 11-3. The short circuit portion 13-3 is laid so as to form an inverted F-type antenna. Further, on the lower surface of the C layer of the wiring board 2, the radiating element 11-4, the feeding portion 12-4 for feeding the radiating element 11-4, and the short-circuit portion 13- for grounding the radiating element 11-4 are provided. 4 are laid to form an inverted F-type antenna. In the formation of the inverted F-type antenna in each layer A, B and C of the wiring board 2, when forming a wiring pattern for each layer in the manufacturing process of the wiring board, it is simultaneously patterned by using a conductive member for each layer. It is preferable to realize.

  The connection portion 14 is provided through the layers A, B, and C of the wiring board 2 and electrically connects the power feeding portions 12-1, 12-2, 12-3, and 12-4. The connecting portion 14 may be formed using, for example, a through hole technique. Alternatively, the connection unit 14 may be realized by connection using a via. Alternatively, the connecting portion 14 may be realized by a conductive member having another configuration and shape. Note that the electrical connection between the RF module and each of the power feeding units 12-1, 12-2, 12-3, and 12-4 is that the power feeding unit in the layer where the RF module is mounted is connected to the power feeding unit to which the RF module is connected. This is preferably realized by connecting electric wires. In the illustrated example, it is assumed that the RF module (not shown) is mounted on the upper surface of the A layer of the wiring board 2, and therefore, in this case, the RF module (not shown) is installed on the upper surface of the A layer of the wiring board 2. The power feeding unit 12-1 is connected to the RF module (not shown) through the power feeding line 16. The feeder line 16 is, for example, a microstrip line.

  Each short-circuit part 13-1, 13-2, 13-3, and 13-4 is connected to the ground line 15 in each layer A, B, and C of the wiring board 2.

  In the present embodiment, the radiating elements 11-1, 11-2, 11-3, and 11-4 have different lengths. Thereby, a wide frequency band can be secured. FIG. 6 is a diagram illustrating the relationship between the length of the radiating element of the antenna and the resonance frequency. In the illustrated example, the case of two radiating elements is shown. If the lengths of the two radiating elements are set to be slightly different, the frequency characteristics will be slightly different. Therefore, if the length of each radiating element is designed so that two resonances occur at a frequency close to the power to be fed to the antenna, the frequency band of the antenna can be expanded. Further, in order to improve antenna characteristics, antenna radiation elements 11-1, 11-2, 11-3 and 11-4, and power feeding units 12-1, 12-2, 12- provided in each layer of the wiring board 2 are provided. 3 and 12-4 and the short-circuit portions 13-1, 13-2, 13-3 and 13-4 overlap each other when the wiring board 2 is viewed in plan view from the upper surface side (or lower surface side). It is preferable to form at a position. In this case, the lengths of the radiating elements 11-1, 11-2, 11-3, and 11-4 are made different for the purpose of improving the frequency band. As can be seen, there are non-overlapping parts in each layer.

  In addition, when the length of each radiating element is made the same, the gain obtained will become large. Therefore, not only the frequency band but also the gain can be adjusted by appropriately combining a set of radiating elements having the same length.

  As the wiring board 2 incorporating the antenna of the present invention, for example, a wiring board in which glass / epoxy substrates are laminated, or a wiring board using a build-up board can be used.

  In the case of a wiring board using a glass / epoxy substrate, for example, each pattern such as an antenna is formed by a subtractive method, or a through hole is formed in the glass / epoxy substrate by drilling, and the inner wall of the through hole is provided. A through-hole (connecting portion 14) is formed by the plating layer, and the wiring board 1 with the built-in antenna is formed.

  In the case of a wiring board using a build-up board, an insulating layer and a wiring layer having an antenna or the like are stacked by a build-up method, and each wiring layer is connected by a via formed in each insulating layer.

  The pattern and via of each wiring layer are formed by, for example, a semi-additive method. The via is formed by forming an opening through which the lower wiring layer is exposed in the insulating layer by laser processing when the semi-additive method is performed, and providing a plating layer on the inner wall of the opening.

  As described above, according to the first embodiment of the present invention, in the multilayer wiring board, the radiating element, the feeding part for feeding power to the radiating element, and the short-circuit part for grounding the radiating element are provided. The F-type antennas are respectively laid on the surface of each layer of the wiring board, and the power feeding part located in each layer is electrically connected by a connecting part provided through each layer of the wiring board. . In the wiring board according to the first embodiment shown in FIGS. 1 to 5, the inverted F-type antennas are formed on all the layers of the wiring board. An antenna may be formed. Alternatively, the radiating element, the feeding portion, and the short-circuit portion may not be formed as an inverted F-type antenna, but may be formed as an inverted L-type antenna in some or all layers.

  FIG. 7 is a perspective view of an antenna and a wiring board according to the second embodiment of the present invention. The antenna 1 according to this embodiment includes two radiating elements 11-a and 11-b, a power feeding unit 12 that feeds power to the radiating elements 11-a and 11-b, and each radiating element 11-a and 11-b. Short circuit part 13 which connects ground plate (GND) 20 is provided. As shown in the figure, an inverted F-type antenna including two radiating elements 11-a and 11-b, a power feeding unit 12, and a short-circuit unit 13 is formed in a three-dimensional manner. Here, the lengths of the radiating elements 11-a and 11-b are different from each other. Thereby, a wide frequency band can be secured. Similarly to the case described in the first embodiment, if the length of each radiating element is the same, the gain is improved. In the present embodiment, the number of radiating elements is two. However, the present invention is not limited to this, and a plurality of radiating elements may be provided.

  The present invention can be applied to an antenna included in a small wireless device. Examples of small wireless devices to which the present invention can be applied include mobile phones, PDAs, IC card readers / writers, audio devices, video devices, game devices, barcode readers, and watches.

  According to the present invention, an antenna that is small in size and high in performance and easy to manufacture and a multilayer wiring board that incorporates the antenna are realized, which contributes to further miniaturization and higher functionality of a wireless small device.

  The present invention also facilitates the process of incorporating the antenna into the wireless small device in the manufacturing process. When forming the wiring pattern of each layer of the wiring board, by simultaneously forming the radiating element, the feeding portion, and the short-circuit portion constituting the antenna, the manufacturing time of the wireless small-sized device including the inverted F-type antenna and consequently the inverted F-type antenna The reduction of the manufacturing cost can be realized.

  Moreover, a wide frequency band is securable by making each radiating element into mutually different length. Since the antenna according to the present invention has a structure in which a plurality of inverted F-type antennas are stacked, the antenna characteristics can be maintained without changing the occupied area of the antenna as compared with a conventional independent inverted-F antenna. Can be improved.

1 is a perspective view of an antenna and a wiring board according to a first embodiment of the present invention. It is a perspective view which shows the inverted F type antenna formed in the upper surface of the uppermost layer among the three-layer wiring boards shown in FIG. It is a perspective view which shows the inverted F type antenna formed in the upper surface of the middle layer among the three-layer wiring boards shown in FIG. It is a perspective view which shows the inverted F type antenna formed in the upper surface of the lowest layer among the three-layer wiring boards shown in FIG. It is a perspective view which shows the inverted F type antenna formed in the lower surface of the lowest layer among the three-layer wiring boards shown in FIG. It is a figure which illustrates the relationship between the length of the radiating element of an antenna, and the resonant frequency. FIG. 6 is a perspective view of an antenna and a wiring board according to a second embodiment of the present invention. It is a figure which shows a general (lambda) / 4 wavelength antenna, (a) shows a monopole antenna, (b) shows an inverted L type antenna, (c) shows an inverted F type antenna. It is a basic principle figure of a general inverted F type antenna. It is a perspective view which illustrates a general solid inverted F type antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Wiring board 11-1, 11-2, 11-3, 11-4, 11-a, 11-b Radiating element 12, 12-1, 12-2, 12-3, 12-4 Feed part 13 , 13-1, 13-2, 13-3, 13-4 Short-circuit part 14 Connection part 15 Ground line 16 Feed line

Claims (11)

An antenna built in a multilayer wiring board,
Radiation elements respectively laid on the surface of each layer of the wiring board;
In order to supply power to each of the radiating elements, a power supply unit laid on the surface of the layer,
In order to ground each of the radiating elements, a short-circuit portion laid on the surface of the layer,
A connection portion that is provided through each layer of the wiring board and electrically connects the power feeding portions;
An antenna comprising:   The antenna according to claim 1, wherein an inverted F-type antenna including the radiating element, the power feeding unit, and the short-circuit unit is formed for each layer.   The antenna according to claim 1, wherein each of the radiating elements has a different length.   The antenna according to claim 1, wherein the radiating element, the power feeding unit, and the short-circuit unit are patterned for each layer.   The antenna according to claim 1, wherein the connection portion includes a through hole. A multilayer wiring board,
An inverted F-type antenna comprising a radiating element, a power feeding part for feeding power to the radiating element, and a short-circuit part for grounding the radiating element, each laid on the surface of each layer of the wiring board An inverted F-type antenna,
A connection portion that is provided through each layer of the wiring board and electrically connects the power feeding portions;
A wiring board comprising:   The wiring board according to claim 6, wherein each of the radiating elements has a different length.   The wiring board according to claim 6, wherein the connection portion includes a through hole.   The wiring board according to claim 6, wherein the radiating element, the power feeding unit, and the short-circuit unit are patterned for each of the layers. A plurality of radiating elements;
A power feeding section for feeding power to each of the radiating elements;
A short-circuit portion connecting each of the radiating elements and the ground plane,
An inverted F-type antenna comprising the plurality of radiating elements, the feeding portion, and the short-circuit portion is formed.   The antenna according to claim 10, wherein each of the radiating elements has a different length.

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